Ceramics composite

ABSTRACT

The present invention relates to a ceramics composite including: a matrix phase including Al 2 O 3  or a substance in which one selected from Sc 2 O 3  and Ga 2 O 3  is incorporated into Al 2 O 3 ; a main phosphor phase formed in the matrix phase and including a substance represented by a general formula A 3 B 5 O 12 :Ce in which A is at least one selected from Y, Gd, Tb, Yb and Lu and B is at least one selected from Al, Ga and Sc; and a CeAl 11 O 18  phase mixed in the matrix phase and the main phosphor phase.

FIELD OF THE INVENTION

The present invention relates to a ceramics composite for wavelengthconversion for use in white or color light emitting diode (LED) and thelike.

BACKGROUND OF THE INVENTION

LED has been applied to cellular phones, various display devices, andthe like owing to characteristics such as electric power saving, longlife, and small size. With an improvement of light emission efficiencythereof, LED has been rapidly coming into wide use also in illuminationuses.

Currently, in white LED illumination, the mainstream is a method whereblue LED and a phosphor emitting a yellow light that is a complementarycolor of blue are used in combination to obtain a white light. As thephosphor, YAG (yttrium aluminum garnet)-based ceramics have beenfrequently employed.

For example, Patent Document 1 describes a ceramics composite having aphosphor phase composed of YAG containing Ce and a matrix phase composedof at least one of Al₂O₃ and AlN. The ceramics composite obtained from aphosphor as above has a simple constitution but an excellent emissionintensity can be obtained.

Patent Document 1: JP-A-2011-12215

SUMMARY OF THE INVENTION

However, in the ceramics composite as described in Patent Document 1, Ceis prone to evaporate during firing at the time of production, variationin emission distribution occurs among portions and production lots, andwavelength conversion becomes inhomogeneous at the time of irradiationwith a blue light, so that chromaticity variation occurs in some cases.

The present invention is contrived for solving the aforementionedtechnical problem, and an object of the invention is to provide aceramics composite which can achieve homogeneous wavelength conversionof a blue light and suppress the variation in emission distribution, inorder to obtain white or color LED which stably emits light withoutchromaticity variation.

The ceramics composite according to the first embodiment of theinvention is a ceramics composite including:

a matrix phase including Al₂O₃ or a substance in which one selected fromSc₂O₃ and Ga₂O₃ is incorporated into Al₂O₃;

a main phosphor phase formed in the matrix phase and including asubstance represented by a general formula A₃B₅O₁₂:Ce in which A is atleast one selected from Y, Gd, Tb, Yb and Lu and B is at least oneselected from Al, Ga and Sc; and

a CeAl₁₁O₁₈ phase mixed in the matrix phase and the main phosphor phase.

By such a constitution, the wavelength conversion at the time ofirradiation with a blue light can be performed homogeneously and thusthe variation in emission distribution can be suppressed.

Moreover, the ceramics composite according to the second embodiment ofthe invention is ceramics composite including:

a matrix phase including Al₂O₃ or a substance in which one selected fromSc₂O₃ and Ga₂O₃ is incorporated into Al₂O₃;

a main phosphor phase formed in the matrix phase and including asubstance represented by a general formula A₃B₅O₁₂:Ce in which A is atleast one selected from Y, Gd, Tb, Yb and Lu and B is at least oneselected from Al, Ga and Sc; and

a CeAl₁₁O₁₈ phase which is mixed only in the main phosphor phase and ispresent in higher density with a prescribed thickness at an outerperipheral part than at an inner part of the main phosphor phase andwhich is contained in an amount of 0.5 to 5.0% by volume in a totalvolume of the ceramics composite.

By such a constitution, the concentration distribution of Ce in the mainphosphor phase can be homogeneously maintained due to a minute amount ofCeAl₁₁O₁₈ phase and thus the variation in emission distribution isefficiently suppressed. Further, an improvement in emission intensitycan be also achieved.

The prescribed thickness of the CeAl₁₁O₁₈ phase is preferably 0.1 to 1.9μm.

By such a constitution, the concentration distribution of Ce in thephosphor phase can be homogeneously maintained and thus the variation inemission distribution can be more efficiently suppressed.

The ceramics composite according to the invention can achievehomogeneous wavelength conversion by the phosphor phase at the time ofirradiation with a blue light and thus the variation in emissiondistribution can be suppressed.

Therefore, the ceramics composite according to the invention can producea stably emitted white light or the like without chromaticity variationby the combination with blue LED.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view showing one example of a phosphor as theceramics composite according to the invention.

FIG. 2 is an A-A cross-sectional view of the phosphor shown in FIG. 1according to the first embodiment of the invention.

FIG. 3 is an A-A cross-sectional view of the phosphor shown in FIG. 1according to the second embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION

The following will describe the ceramics composite according to theinvention in detail with reference to Drawings.

FIG. 1 shows one example of an appearance of a phosphor as the ceramicscomposite according to an embodiment of the invention. An A-Across-sectional view according to the first embodiment is shown in FIG.2 and an A-A cross-sectional view according to the second embodiment isshown in FIG. 3.

As shown in FIG. 2, the ceramics composite 1 according to the firstembodiment of the invention includes a matrix phase 2 including Al₂O₃ ora substance in which one selected from Sc₂O₃ and Ga₂O₃ is incorporatedinto Al₂O₃; a main phosphor phase 3 formed in the matrix phase 2 andincluding a substance represented by a general formula A₃B₅O₁₂:Ce inwhich A is at least one selected fro Y, Gd, Tb, Yb and Lu and B is atleast one selected from Al, Ga and Sc; and a CeAl₁₁O₁₈ phase 4 mixed inthe matrix phase 2 and the main phosphor phase 3.

The matrix phase 2 of the ceramics composite includes Al₂O₃ or asubstance in which one selected from Sc₂O₃ and Ga₂O₃ is incorporatedinto Al₂O₃.

Since Al₂O₃ ceramics or ceramics in which one selected from Sc₂O₃ andGa₂O₃ is incorporated into Al₂O₃ ceramics are excellent in heatresistance, weather resistance, and heat radiation as well as excellentin translucency, the main phosphor phase 3 can be suitably mixed in thematrix phase 2 and the ceramics can transmit a light emitted from themain phosphor phase 3 and further are suitable materials also from theviewpoint of durability.

The main phosphor phase 3 includes a substance represented by thegeneral formula A₃B₅O₁₂:Ce in which A is at least one selected from Y,Gd, Tb, Yb and Lu and B is at least one selected from Al, Ga and Sc.

As above, the ceramics composite according to the invention includes themain phosphor phase 3 using Ce as an activator and Ce is prone toevaporate upon firing at the time of production, whereby thechromaticity variation occurs among the portions and production lots ofthe ceramics composite.

For solving the above problem, in the ceramics composite according tothe invention, for example, the CeAl₁₁O₁₈ phase 4 is mixed in the matrixphase 2 and the main phosphor phase 3 in the embodiment as shown in FIG.2.

By such a constitution, the evaporated amount of Ce in the main phosphorphase can be compensated by Ce in the mixed CeAl₁₁O₁₈ phase, so that itis considered that the concentration distribution of Ce in the mainphosphor phase 3 can be homogeneously maintained and thus the variationin emission distribution is suppressed.

Moreover, in the ceramics composite 1 according to the second embodimentof the invention, the matrix phase 2 and the main phosphor phase 3 havethe same constitutions as those in the ceramics composite according tothe first embodiment, respectively, but, as shown in FIG. 3, theCeAl₁₁O₁₈ phase 4 is mixed only in the main phosphor phase 3 and ispresent in higher density with a prescribed thickness at an outerperipheral part than at an inner part of the main phosphor phase 3. Asabove, the CeAl₁₁O₁₈ phase 4 is present in higher density with aprescribed thickness at an outer peripheral part than at an inner partof the main phosphor phase 3, so that the concentration distribution ofCe in the main phosphor phase 3 can be further homogeneously maintainedowing to a minute amount of the CeAl₁₁O₁₈ phase 4 and thus the variationin emission distribution can be further suppressed.

In the ceramics composite according to the first embodiment, theCeAl₁₁O₁₈ phase 4 is preferably contained in an amount of 0.5 to 5.0% byvolume in the total volume of the ceramics composite. Additionally, Inceramics composite according to the second embodiment, the CeAl₁₁O₁₈phase 4 is contained in an amount of 0.5 to 5.0% by volume in the totalvolume of the ceramics composite.

In the case where the volume is less than 0.5% by volume, portions whereCe evaporated upon firing is not compensated are frequently generatedand the chromaticity variation is not sufficiently suppressed.

On the other hand, in the case where the volume exceeds 5.0% by volume,the CeAl₁₁O₁₈ phase 4 absorbs fluorescence and thus the emissionefficiency decreases.

Incidentally, the volume of the CeAl₁₁O₁₈ phase is determined byanalyzing the composition of arbitrary cross-section of the ceramicscomposite on an electron probe microanalyzer (EPMA), calculatingconcentration distributions of Ce, Al, A (at least one selected from Y,Gd, Tb, Yb and Lu) and B (at least one selected from Al, Ga and Sc), andcalculating the ratio of the CeAl₁₁O₁₈ phase 4.

The CeAl₁₁O₁₈ phase 4 is preferably contained in an amount of 0.5 to1.2% by volume in the total volume of the ceramics composite.

By controlling the volume to such a range, the emission intensity isimproved and further, the variation in emission distribution can befurther suppressed.

The thickness of the CeAl₁₁O₁₈ phase 4 is preferably 0.1 to 1.9 μm.

When the phase has such thickness, Ce can be more effectivelycompensated by a minute amount of the CeAl₁₁O₁₈ phase and theconcentration distribution of Ce in the main phosphor phase 3 can behomogeneously maintained, so that a high efficiency can be kept and thevariation in emission distribution can be more effectively suppressed.

In the case where the thickness is less than 0.1 μm, there is a concernthat a portion where Ce is not present in high density is generated atan outer peripheral part of the main phosphor phase 3.

On the other hand, in the case where the thickness exceeds 1.9 μm, theCeAl₁₁O₁₈ phase 4 absorbs fluorescence and there is a concern that theemission efficiency decreases, so that the concentration distribution ofCe in the main phosphor phase 3 cannot be homogeneously maintained andthus there is a concern that the variation of emission distributionbecomes worse.

In this regard, the thickness is determined by composition analysis onEPMA and calculation with specifying the CeAl₁₁O₁₈ phase 4.

Incidentally, the content ratio of Ce, which is an activator on the mainphosphor phase 3, to A represented by the general formula A₃B₅O₁₂:Ce (Ais at least one selected from Y, Gd, Tb, Yb and Lu and B is at least oneselected from Al, Ga and Sc) is preferably 0.001 to 0.05 in terms of anatomic ratio.

When the content ratio of Ce is controlled to a value within the aboverange, fluorescence having a suitable wavelength is generated byirradiation with a blue light and an emission color such as practicalwhite color can be obtained.

In the case where the content ratio of Ce is less than 0.001, asufficient CeAl₁₁O₁₈ phase cannot be formed and there is a concern thatvariation occurs in the emission distribution.

On the other hand, when the content ratio of Ce exceeds 0.05, theCeAl₁₁O₁₈ phase is excessively formed and there is a concern that theemission intensity decreases.

The linear transmittance at 600 nm of the ceramics composite ispreferably 0.5% or more and less than 5,0%.

In the case where the linear transmittance is less than 0.5%, the ratioof a light extracted from the light outgoing surface side decreases, sothat there is a concern that the emission intensity decreases.

On the other hand, in the case where the linear transmittance is 5.0% ormore, diffusion of a blue light radiated from the light emitting elementbecomes insufficient, so that the blue light and the yellow light areseparated and there is a concern that the variation in emissiondistribution occurs.

The linear transmittance of the ceramics composite for use in the samelight emitting element at 600 nm is preferably ±0.2% or less.

By such a constitution, a balance between a blue transmitted light and ayellow fluorescent can be homogenized, so that the chromaticityvariation can be further decreased.

In the case where the linear transmittance is larger than ±0.2%, adiffusion degree of the blue light varies among portions, so that thereis a concern that the chromaticity variation occurs.

EXAMPLES

The following will describe the invention in further detail based onExamples but the invention should not be construed as being limited tothe following Examples.

Preparation of Ceramics Composite According to First Embodiment

A CeO₂ powder (average particle size of 0.3 μm, purity of 99.9%), a Y₂O₃powder (average particle size of 0.9 μm, purity of 99.9%), an Al₂O₃powder (average particle size of 0.3 μm, purity of 99.9%) were used asraw materials.

First, the CeO₂ powder, the Y₂O₃ powder, and the Al₂O₃ powder were mixedin a prescribed ratio and ethanol and an acrylic binder were addedthereto. Then, the whole was mixed in a ball mill using alumina ballsfor 20 hours to prepare a slurry. From the slurry, a granulation powderhaving an average particle size of 20 μm was prepared using a spraydrier (Preparation 1).

Then, ethanol and an acrylic binder were added only to the Al₂O₃ powderand the whole was mixed in a ball mill using alumina balls for 20 hoursto prepare a slurry. From the slurry, a granulation powder having anaverage particle size of 50 μm was prepared using a spray drier(Preparation 2).

After two kinds of the prepared granulation powders were dry mixed, theresulting mixture was subjected to uniaxial molding at 10 MPa andsubsequently to cold isostatic press (CIP) at 100 MPa to form a formedarticle. After degreased at 600° C. in the air, the resulting formedarticle was fired under a vacuum atmosphere to prepare a ceramicscomposite.

On this occasion, by changing the amounts of the CeO₂ powder, the Al₂O₃powder powder, and the Y₂O₃ powder, a plurality of ceramics compositeseach having a changed volume ratio of CeAl₁₁O₁₈ were prepared.

Moreover, a plurality of ceramics composites each being different in thecomposition and having a changed volume ratio of CeAl₁₁O₁₈ were preparedin the same manner except that at least one selected from a Gd₂O₃ powder(average particle size of 0.3 μm, purity of 99.9%), a Tb₂O₃ powder(average particle size of 0.3 μm, purity of 99.9%), a Yb₂O₃ powder(average particle size of 0.3 μm, purity of 99.9%) and a Lu₂O₃ powder(average particle size of 0.3 μm, purity of 99.9%) or at least oneselected from a Ga₂O₃ powder (average particle size of 0.3 μm, purity of99.9%) and an Sc₂O₃ powder (average particle size of 0.3 μm, purity of99.9%) was further mixed in a prescribed ratio at Preparation 1, or oneselected from an Sc₂O₃ powder (average particle size of 0.3 μm, purityof 99.9%) and a Ga₂O₃ powder (average particle size of 0.3 μm, purity of99.9%) was further mixed in a prescribed ratio at Preparation 2.

For the prepared ceramics composites, various kinds of evaluations shownin the following were performed.

(Evaluation of Physical Properties and Optical Properties of CeramicsComposite) (1) Volume Composition

After a crystal phase of the ceramics composite was investigated bypowder X-ray diffraction, a cross-section was polished and was subjectedto composition analysis on EPMA.

Moreover, for the sample under the same conditions as in the above (1),evaluation shown in the following (2) to (5) was performed.

(2) Emission Intensity

For a sample processed into a size of 7.5 mm×7.5 mm×0.1 mm in thickness,after an emitted light when blue LED having a peak wavelength of 473 nmwas used as an excitation light was collected at an integrating sphere,a spectrum was measured using a spectroscope (USB4000 fibermulti-channel spectroscope manufactured by Ocean Optics, Inc.) and theemission intensity normalized with an absorption amount was determinedfrom the resulting spectrum.

(3) Color Unevenness

A sample processed into a size of 1 mm×1 mm×0.08 mm was fixed onto anblue LED element (emission region: 1 mm×1 mm, emission wavelength: 460nm) with a silicone resin to thereby mount the sample on the blue LEDand the color unevenness of an emitted light from a lateral side of theLED element was observed.

(4) Chromaticity Variation

For a sample processed into a size of 60 mm×60 mm×0.08 mm in thickness,a blue light having a diameter of 1 mm was applied from a lower part ofthe sample and an illuminometer (T-10M manufactured by Konica MinoltaHoldings, Inc.) was provided on an upper part. Chromaticity was measuredat 5 mm intervals (121 points in total) in a region of 50 mm×50 mm at acenter of the sample and the chromaticity variation (ΔCIE_(x)) wasevaluated.

(5) Heat Conductivity

For a sample processed into a size of 10 mm in diameterx2 mm inthickness, the heat conductivity was measured by laser flash method.

In Tables 1 and 2, test conditions ((1) volume composition) and testresults ((2) emission intensity, (4) chromaticity variation) in Test 1are shown.

TABLE 1 Constitution Effect Volume ratio of Chromaticity Average valueof Average value of Main phosphor CeAl₁₁O₁₈ phase Emission variationemission chromaticity Matrix phase phase (% by volume) intensity (ΔCEX)intensity variation Comparative Example 1 Al₂O₃, Sc₂O₃ Lu₃Sc₂Al₃O₁₂:Ce5.1 90 0.0018 91.7 0.00171 Comparative Example 2 Al₂O₃ Y₃Al₅O₁₂:Ce 5.296 0.0014 Comparative Example 3 Al₂O₃, Ga₂O₃ Tb₃Ga₁Al₄O₁₂:Ce 5.2 970.0018 Comparative Example 4 Al₂O₃, Ga₂O₃ Y₃Ga₁Al₄O₁₂:Ce 5.2 93 0.0019Comparative Example 5 Al₂O₃, Sc₂O₃ Lu₃Sc₁Al₄O₁₂:Ce 5.2 94 0.0017Comparative Example 6 Al₂O₃ Yb₃Al₅O₁₂:Ce 5.3 90 0.0011 ComparativeExample 7 Al₂O₃ Y_(0.5)Gd_(2.5)Al₅O₁₂:Ce 5.3 95 0.002 ComparativeExample 8 Al₂O₃, Ga₂O₃ Yb₃Ga₁Al₄O₁₂:Ce 5.6 95 0.0022 Comparative Example9 Al₂O₃ Y_(1.5)Gd_(1.5)Al₅O₁₂:Ce 5.8 93 0.0017 Comparative Example 10Al₂O₃, Sc₂O₃ Y₃Sc₁Al₄O₁₂:Ce 5.8 89 0.0011 Comparative Example 11 Al₂O₃,Ga₂O₃ Gd₃Ga₁Al₄O₁₂:Ce 5.9 92 0.0011 Comparative Example 12 Al₂O₃, Ga₂O₃Lu₃Ga₁Al₄O₁₂:Ce 6.2 91 0.0024 Comparative Example 13 Al₂O₃, Sc₂O₃Y₃Sc₂Al₃O₁₂:Ce 6.4 88 0.0021 Comparative Example 14 Al₂O₃ Tb₃Al₅O₁₂:Ce6.5 92 0.0013 Comparative Example 15 Al₂O₃ Lu₃Al₅O₁₂:Ce 7.3 80 0.0021Example 1 Al₂O₃ Yb₃Al₅O₁₂:Ce 5 101 0.0012 102.1 0.00176 Example 2 Al₂O₃Y_(1.5)Gd_(1.5)Al₅O₁₂:Ce 5 103 0.0013 Example 3 Al₂O₃ Y₃Al₅O₁₂:Ce 5 1010.0015 Example 4 Al₂O₃ Tb₃Al₅O₁₂:Ce 5 103 0.0017 Example 5 Al₂O₃Y_(0.5)Gd_(2.5)Al₅O₁₂:Ce 5 102 0.0021 Example 6 Al₂O₃ Lu₃Al₅O₁₂:Ce 5 1000.0022 Example 7 Al₂O₃, Ga₂O₃ Gd₃Ga₁Al₄O₁₂:Ce 5 104 0.0013 Example 8Al₂O₃, Ga₂O₃ Y₃Ga₁Al₄O₁₂:Ce 5 102 0.0017 Example 9 Al₂O₃, Ga₂O₃Tb₃Ga₁Al₄O₁₂:Ce 5 102 0.0017 Example 10 Al₂O₃, Ga₂O₃ Lu₃Ga₁Al₄O₁₂:Ce 5102 0.002 Example 11 Al₂O₃, Ga₂O₃ Yb₃Ga₁Al₄O₁₂:Ce 5 101 0.0021 Example12 Al₂O₃, Sc₂O₃ Y₃Sc₁Al₄O₁₂:Ce 5 106 0.0015 Example 13 Al₂O₃, Sc₂O₃Lu₃Sc₁Al₄O₁₂:Ce 5 101 0.0018 Example 14 Al₂O₃, Sc₂O₃ Lu₃Sc₂Al₃O₁₂:Ce 5103 0.0019 Example 15 Al₂O₃, Sc₂O₃ Y₃Sc₂Al₃O₁₂:Ce 5 100 0.0024

TABLE 2 Constitution Effect Volume Average Average ratio of Chromaticityvalue of value of Matrix Main phosphor CeAl₁₁O₁₈ phase Emissionvariation emission chromaticity phase phase (% by volume) intensity(ΔCEX) intensity variation Example 16 Al₂O₃, Sc₂O₃ Y₃Sc₁Al₄O₁₂:Ce 1.2121 0.0013 111.9 0.00165 Example 17 Al₂O₃, Sc₂O₃ Lu₃Sc₁Al₄O₁₂:Ce 1.2 1180.0021 Example 18 Al₂O₃, Sc₂O₃ Y₃Sc₂Al₃O₁₂:Ce 1.1 120 0.0015 Example 19Al₂O₃, Ga₂O₃ Gd₃GA₁Al₄O₁₂:Ce 1.1 108 0.0021 Example 20 Al₂O₃Tb₃Al₅O₁₂:Ce 0.9 109 0.0014 Example 21 Al₂O₃ Y_(0.5)Gd_(2.5)Al₅O₁₂:Ce0.8 110 0.0016 Example 22 Al₂O₃, Ga₂O₃ Lu₃Ga₁Al₄O₁₂:Ce 0.8 105 0.0021Example 23 Al₂O₃, Ga₂O₃ Y₃GA₁Al₄O₁₂:Ce 0.7 109 0.0014 Example 24 Al₂O₃Y_(1.5)Gd_(1.5)Al₅O₁₂:Ce 0.7 109 0.0016 Example 25 Al₂O₃, Ga₂O₃Yb₃GA₁Al₄O₁₂:Ce 0.6 104 0.0013 Example 26 Al₂O₃ Lu₃Al₅O₁₂:Ce 0.6 1250.0015 Example 27 Al₂O₃, Sc₂O₃ Lu₃Sc₂Al₃O₁₂:Ce 0.6 119 0.002 Example 28Al₂O₃ Y₃Al₅O₁₂:Ce 0.5 110 0.0015 Example 29 Al₂O₃, Ga₂O₃ Tb₃Ga₁Al₄O₁₂:Ce0.5 102 0.0016 Example 30 Al₂O₃ Yb₃Al₅O₁₂:Ce 0.5 110 0.0017 ComparativeExample 16 Al₂O₃ Y_(0.5)Gd_(2.5)Al₅O₁₂:Ce 0 111 0.012 113.2 0.01847Comparative Example 17 Al₂O₃ Yb₃Al₅O₁₂:Ce 0 112 0.012 ComparativeExample 18 Al₂O₃ Y_(1.5)Gd_(1.5)Al₅O₁₂:Ce 0 112 0.015 ComparativeExample 19 Al₂O₃ Tb₃Al₅O₁₂:Ce 0 112 0.015 Comparative Example 20 Al₂O₃Y₃Al₅O₁₂:Ce 0 113 0.015 Comparative Example 21 Al₂O₃ Lu₃Al₅O₁₂:Ce 0 1230.021 Comparative Example 22 Al₂O₃, Ga₂O₃ Tb₃Ga₁Al₄O₁₂:Ce 0 104 0.012Comparative Example 23 Al₂O₃, Ga₂O₃ Gd₃Ga₁Al₄O₁₂:Ce 0 108 0.014Comparative Example 24 Al₂O₃, Ga₂O₃ Y₃Ga₁Al₄O₁₂:Ce 0 110 0.014Comparative Example 25 Al₂O₃, Ga₂O₃ Yb₃Ga₁Al₄O₁₂:Ce 0 105 0.021Comparative Example 26 Al₂O₃, Ga₂O₃ Lu₃Ga₁Al₄O₁₂:Ce 0 103 0.026Comparative Example 27 Al₂O₃, Sc₂O₃ Lu₃Sc₂Al₃O₁₂:Ce 0 120 0.021Comparative Example 28 Al₂O₃, Sc₂O₃ Y₃Sc₂Al₃O₁₂:Ce 0 121 0.023Comparative Example 29 Al₂O₃, Sc₂O₃ Lu₃Sc₁Al₄O₁₂:Ce 0 119 0.026Comparative Example 30 Al₂O₃, Sc₂O₃ Y₃Sc₁Al₄O₁₂:Ce 0 125 0.03

Incidentally, in (1) volume composition, as a result of calculating thevolume ratio of Y₃Al₅O₁₂:Ce that is a main phosphor phase, the volumeratio of Al₂O₃ that is a matrix phase, and the volume ratio of theCeAl₁₁O₁₈ phase in the ceramics composite, it was confirmed that themain phosphor phase is mixed in a ratio of 20% by volume to 25% byvolume and the CeAl₁₁O₁₈ phase is mixed in the matrix phase and the mainphosphor phase.

As shown in Table 1, it is recognized that the chromaticity variation(ΔCIE_(x)) decreases to 1/10 or less in the case where the volume ratioof the CeAl₁₁O₁₈ phase exceeds 0.5% by volume (Examples 1 to 30,Comparative Examples 1 to 15) as compared with the case where the volumeratio of the CeAl₁₁O₁₈ phase is 0% by volume (Comparative Examples 16 to30). Incidentally, in the case where the volume ratio of the CeAl₁₁O₁₈phase exceeds 5% by volume (Comparative Examples 1 to 15), it isrecognized that the emission intensity tends to decrease.

Furthermore, in the case where the volume ratio of the CeAl₁₁O₁₈ phaseis 0.5 to 1.2% by volume (Examples 16 to 30), it is recognized that theemission intensity is improved and further the chromaticity variation(ΔCIE_(x)) also decreases as compared with the case where the volumeratio is 5% by volume (Examples 1 to 15).

Incidentally, with regard to (3) color unevenness, as compared with acommercially available YAG:Ce phosphor (P46-Y3 manufactured by ChemicalOptronics), it is recognized that the color unevenness is small underall conditions. Moreover, with regard to (5) heat conductivity, as aresult of evaluation targeting 18 W/(m·K) or more from the viewpoint ofa heat radiation effect, it is recognized that the heat conductivity isas high as 24 W/(m·K) under all conditions.

[Test 2] Preparation of Ceramics Composite According to SecondEmbodiment

A CeO₂ powder (average particle size of 0.3 μm, purity of 99.9%), a Y₂O₃powder (average particle size of 0.9 μm, purity of 99.9%), and an Al₂O₃powder (average particle size of 0.3 μm, purity of 99.9%) were used asraw materials.

First, individual raw material powders were mixed in a prescribed ratio,ethanol was added thereto, and the whole was mixed in a ball mill usingalumina balls for 20 hours to prepare a slurry. From the slurry, agranulation powder having an average particle size of 20 μm was preparedusing a spray drier (Preparation 3).

The prepared granulation powder was fired at 1700° C. in the air toobtain a Y₃Al₅O₁₂:Ce powder containing CeAl₁₁O₁₈.

Then, ethanol and an acrylic binder were added to the obtainedY₃Al₅O₁₂:Ce powder containing CeAl₁₁O₁₈ and the Al₂O₃ powder and thewhole was mixed in a ball mill using alumina balls for 20 hours toprepare a slurry. From the slurry, a granulation powder having anaverage particle size of 50 μm was prepared using a spray drier.

The granulation powder was subjected to uniaxial molding at 10 MPa andthen cold isostatic press (CIP) at 100 MPa to form a formed article.After degreased at 600° C. in the air, the resulting formed article wasfired under a vacuum atmosphere to prepare a ceramics composite.Moreover, a plurality of ceramics composites each being different in thecomposition and having a changed volume ratio of CeAl₁₁O₁₈ were preparedin the same manner except that at least one selected from a Gd₂O₃ powder(average particle size of 0.3 μm, purity of 99.9%), a Tb₂O₃ powder(average particle size of 0.3 μm, purity of 99.9%), a Yb₂O₃ powder(average particle size of 0.3 μm, purity of 99.9%), and a Lu₂O₃ powder(average particle size of 0.3 μm, purity of 99.9%) or at least oneselected from a Ga₂O₃ powder (average particle size of 0.3 μm, purity of99.9%) and an Sc₂O₃ powder (average particle size of 0.3 μm, purity of99.9%) was further mixed in a prescribed ratio, or at least one selectedfrom an Sc₂O₃ powder (average particle size of 0.3 μm, purity of 99.9%)and a Ga₂O₃ powder (average particle size of 0.3 μm, purity of 99.9%)was further mixed in a prescribed ratio at Preparation 3.

For the prepared ceramics composites, various kinds of evaluations wereperformed in the same manner as in Test 1.

In Tables 3 to 5, test conditions ((1) volume composition) and testresults ((2) emission intensity, (4) chromaticity variation) in Test 2are shown.

TABLE 3 Constitution Effect Volume Average Average ratio of Chromaticityvalue value Main phosphor CeAl₁₁O₁₈ phase Thickness Emission variationof emission of chromatic Matrix phase phase (% by volume) (μm) intensity(ΔCEX) intensity variation Comparative Example 31 Al₂O₃Y_(1.5)Gd_(1.5)Al₅O₁₂:Ce 2.2 0.08 111 0.0017 113.6 0.00223 ComparativeExample 32 Al₂O₃ Y_(0.5)Gd_(2.5)Al₅O₁₂:Ce 2.2 0.08 112 0.0021Comparative Example 33 Al₂O₃ Yb₃Al₅O₁₂:Ce 2.3 0.08 114 0.0021Comparative Example 34 Al₂O₃ Lu₃Al₅O₁₂:Ce 2.1 0.08 125 0.0023Comparative Example 35 Al₂O₃ Y₃Al₅O₁₂:Ce 2.3 0.09 111 0.0015 ComparativeExample 36 Al₂O₃ Tb₃Al₅O₁₂:Ce 2.1 0.09 113 0.0015 Comparative Example 37Al₂O₃, Ga₂O₃ Y₃Ga₁Al₄O₁₂:Ce 2.5 0.08 110 0.0025 Comparative Example 38Al₂O₃, Ga₂O₃ Gd₃Ga₁Al₄O₁₂:Ce 2.1 0.08 112 0.0021 Comparative Example 39Al₂O₃, Ga₂O₃ Tb₃Ga₁Al₄O₁₂:Ce 2.5 0.08 107 0.0024 Comparative Example 40Al₂O₃, Ga₂O₃ Yb₃Ga₁Al₄O₁₂:Ce 2.1 0.08 107 0.0027 Comparative Example 41Al₂O₃, Ga₂O₃ Lu₃Ga₁Al₄O₁₂:Ce 2.3 0.08 108 0.0027 Comparative Example 42Al₂O₃, Sc₂O₃ Y₃Sc₂Al₃O₁₂:Ce 2.4 0.08 121 0.0021 Comparative Example 43Al₂O₃, Sc₂O₃ Y₃Sc₁Al₄O₁₂:Ce 2.6 0.08 116 0.0024 Comparative Example 44Al₂O₃, Sc₂O₃ Lu₃Sc₂Al₃O₁₂:Ce 2.7 0.08 118 0.0025 Comparative Example 45Al₂O₃, Sc₂O₃ Lu₃Sc₁Al₄O₁₂:Ce 2.1 0.08 119 0.0029 Example 31 Al₂O₃Y₃Al₅O₁₂:Ce 2.4 0.1 110 0.0011 111.9 0.00111 Example 32 Al₂O₃Y_(1.5)Gd_(1.5)Al₅O₁₂:Ce 2.3 0.1 109 0.001 Example 33 Al₂O₃Y_(0.5)Gd_(2.5)Al₅O₁₂:Ce 2.6 0.1 110 0.0009 Example 34 Al₂O₃Tb₃Al₅O₁₂:Ce 2.3 0.1 109 0.0011 Example 35 Al₂O₃ Yb₃Al₅O₁₂:Ce 2.4 0.1110 0.0013 Example 36 Al₂O₃ Lu₃Al₅O₁₂:Ce 2.4 0.1 125 0.0013 Example 37Al₂O₃, Ga₂O₃ Y₃Ga₁Al₄O₁₂:Ce 2.3 0.1 109 0.0011 Example 38 Al₂O₃, Ga₂O₃Gd₃Ga₁Al₄O₁₂:Ce 2.1 0.1 108 0.0011 Example 39 Al₂O₃, Ga₂O₃Tb₃Ga₁Al₄O₁₂:Ce 2.7 0.1 102 0.001 Example 40 Al₂O₃, Ga₂O₃Yb₃Ga₁Al₄O₁₂:Ce 2.7 0.1 104 0.0012 Example 41 Al₂O₃, Ga₂O₃Lu₃Ga₁Al₄O₁₂:Ce 2.1 0.1 105 0.0011 Example 42 Al₂O₃, Sc₂O₃Y₃Sc₂Al₃O₁₂:Ce 2.6 0.1 120 0.0012 Example 43 Al₂O₃, Sc₂O₃ Y₃Sc₁Al₄O₁₂:Ce2.1 0.1 121 0.001 Example 44 Al₂O₃, Sc₂O₃ Lu₃Sc₂Al₃O₁₂:Ce 2.3 0.1 1190.0011 Example 45 Al₂O₃, Sc₂O₃ Lu₃Sc₁Al₄O₁₂:Ce 2.1 0.1 118 0.0012

TABLE 4 Constitution Effect Volume ratio of Chromaticity Average valueof Average value of Main phosphor CeAl₁₁O₁₈ phase Thickness Emissionvariation emission chromatic Matrix phase phase (% by volume) (μm)intensity (ΔCEX) intensity variation Example 46 Al₂O₃ Y₃Al₅O₁₂:Ce 4.2 1102 0.001 102.4 0.00080 Example 47 Al₂O₃ Y_(1.5)Gd_(1.5)Al₅O₁₂:Ce 4.1 1102 0.0009 Example 48 Al₂O₃ Y_(0.5)Gd_(2.5)Al₅O₁₂:Ce 3.9 1 104 0.0007Example 49 Al₂O₃ Tb₃Al₅O₁₂:Ce 3.9 1 102 0.0006 Example 50 Al₂O₃Yb₃Al₅O₁₂:Ce 3.9 1 105 0.0007 Example 51 Al₂O₃ Lu₃Al₅O₁₂:Ce 3.8 1 1010.0005 Example 52 Al₂O₃, Ga₂O₃ Y₃Ga₁Al₄O₁₂:Ce 3.9 1 101 0.0008 Example53 Al₂O₃, Ga₂O₃ Gd₃Ga₁Al₄O₁₂:Ce 4.2 1 103 0.0006 Example 54 Al₂O₃, Ga₂O₃Tb₃Ga₁Al₄O₁₂:Ce 4.1 1 102 0.0009 Example 55 Al₂O₃, Ga₂O₃ Yb₃Ga₁Al₄O₁₂:Ce4.2 1 105 0.0008 Example 56 Al₂O₃, Ga₂O₃ Lu₃Ga₁Al₄O₁₂:Ce 4.3 1 1020.0007 Example 57 Al₂O₃, Sc₂O₃ Y₃Sc₂Al₃O₁₂:Ce 4.1 1 101 0.001 Example 58Al₂O₃, Sc₂O₃ Y₃Sc₁Al₄O₁₂:Ce 4.1 1 102 0.001 Example 59 Al₂O₃, Sc₂O₃Lu₃Sc₂Al₃O₁₂:Ce 4 1 103 0.0008 Example 60 Al₂O₃, Sc₂O₃ Lu₃Sc₁Al₄O₁₂:Ce3.9 1 101 0.001 Example 61 Al₂O₃ Y_(0.5)Gd_(2.5)Al₅O₁₂:Ce 4.8 1.1 1060.0009 103.9 0.00068 Example 62 Al₂O₃, Sc₂O Lu₃Sc₂Al₃O₁₂:Ce 4.9 1.1 1030.0006 Example 63 Al₂O₃ Y₃Al₅O₁₂:Ce 4.7 1.2 102 0.0009 Example 64 Al₂O₃,Ga₂O₃ Y₃Ga₁Al₄O₁₂:Ce 4.2 1.2 102 0.0006 Example 65 Al₂O₃, Ga₂O₃Tb₃Ga₁Al₄O₁₂:Ce 4.8 1.2 107 0.0007 Example 66 Al₂O₃, Sc₂O₃Y₃Sc₂Al₃O₁₂:Ce 4.3 1.2 107 0.0008 Example 67 Al₂O₃Y_(1.5)Gd_(1.5)Al₅O₁₂:Ce 4.7 1.3 104 0.001 Example 68 Al₂O₃, Ga₂O₃Yb₃Ga₁Al₄O₁₂:Ce 4.9 1.3 102 0.0004 Example 69 Al₂O₃, Sc₂O₃Y₃Sc₁Al₄O₁₂:Ce 4.2 1.3 104 0.0006 Example 70 Al₂O₃ Lu₃Al₅O₁₂:Ce 4.9 1.4106 0.0007 Example 71 Al₂O₃, Sc₂O₃ Lu₃Sc₁Al₄O₁₂:Ce 4.9 1.4 106 0.0009Example 72 Al₂O₃ Tb₃Al₅O₁₂:Ce 4.6 1.5 102 0.0005 Example 73 Al₂O₃Yb₃Al₅O₁₂:Ce 4.8 1.6 101 0.0006 Example 74 Al₂O₃, Ga₂O₃ Gd₃Ga₁Al₄O₁₂:Ce4.7 1.7 104 0.0005 Example 75 Al₂O₃, Ga₂O₃ Lu₃Ga₁Al₄O₁₂:Ce 4.6 1.9 1030.0005

TABLE 5 Constitution Effect Volume Average Average ratio of Chromaticityvalue value Main phosphor CeAl₁₁O₁₈ phase Thickness Emission variationof emission of chromatic Matrix phase phase (% by volume) (μm) intensity(ΔCEX) intensity variation Comparative Example 46 Al₂O₃Y_(0.5)Gd_(2.5)Al₅O₁₂:Ce 5.5 2.0 96 0.0003 93.5 0.00055 ComparativeExample 47 Al₂O₃, Sc₂O₃ Lu₃Sc₂Al₃O₁₂:Ce 5.8 2.5 92 0.0007 ComparativeExample 48 Al₂O₃ Y₃Al₅O₁₂:Ce 5.3 2.3 91 0.0002 Comparative Example 49Al₂O₃, Ga₂O₃ Y₃Ga₁Al₄O₁₂:Ce 5.4 2.2 96 0.0005 Comparative Example 50Al₂O₃, Ga₂O₃ Tb₃Ga₁Al₄O₁₂:Ce 6.1 2.6 94 0.0005 Comparative Example 51Al₂O₃, Sc₂O₃ Y₃Sc₂Al₃O₁₂:Ce 5.3 2.3 96 0.0009 Comparative Example 52Al₂O₃ Y_(1.5)Gd_(1.5)Al₅O₁₂:Ce 5.5 2.6 92 0.0008 Comparative Example 53Al₂O₃, Ga₂O₃ Yb₃Ga₁Al₄O₁₂:Ce 5.2 2.3 93 0.0005 Comparative Example 54Al₂O₃, Sc₂O₃ Y₃Sc₁Al₄O₁₂:Ce 5.7 2.1 96 0.0003 Comparative Example 55Al₂O₃ Lu₃Al₅O₁₂:Ce 5.2 2.1 97 0.0006 Comparative Example 56 Al₂O₃, Sc₂O₃Lu₃Sc₁Al₄O₁₂:Ce 5.1 2.7 91 0.0008 Comparative Example 57 Al₂O₃Tb₃Al₅O₁₂:Ce 5.8 2.5 90 0.0005 Comparative Example 58 Al₂O₃ Yb₃Al₅O₁₂:Ce5.8 2.4 95 0.0002 Comparative Example 59 Al₂O₃, Ga₂O₃ Gd₃Ga₁Al₄O₁₂:Ce5.2 2.2 92 0.0007 Comparative Example 60 Al₂O₃, Ga₂O₃ Lu₃Ga₁Al₄O₁₂:Ce5.4 2.1 91 0.0008

Incidentally, in (1) volume composition, as a result of calculating thevolume ratio of Y₃Al₅O₁₂:Ce that is a main phosphor phase, the volumeratio of Al₂O₃ that is a matrix phase, and the volume ratio of theCeAl₁₁O₁₈ phase in the ceramics composite, it was confirmed that themain phosphor phase is mixed in 20% by volume to 25% by volume and theCeAl₁₁O₁₈ phase is mixed only in the main phosphor phase and is presentat higher density in prescribed thickness at an outer peripheral partthan at an inner part of the main phosphor phase.

As shown in Table 2, it is recognized that the chromaticity variation(ΔCIE_(x)) becomes twice or more times worse in the case where theprescribed thickness of the CeAl₁₁O₁₈ phase is less than 0.1 mm(Comparative Examples 31 to 45) than in the case where the thickness is0.1 mm or more (Examples 31 to 75).

Moreover, it is recognized that the chromaticity variation (ΔCIE_(x)) isimproved in the case where the CeAl₁₁O₁₈ phase is present at higherdensity with a prescribed thickness at an outer peripheral part than atan inner part of the main phosphor phase (Examples 31 to 75) as comparedwith the case where the phase is mixed in the matrix phase and the mainphosphor phase (Examples 1 to 30).

Furthermore, in the case where the prescribed thickness of the CeAl₁₁O₁₈phase is larger than 1.9 mm (Comparative Examples 46 to 60), it isrecognized that the emission intensity tends to decrease.

Incidentally, with regard to (3) color unevenness, as compared with acommercially available YAG:Ce phosphor (P46-Y3 manufactured by ChemicalOptronics), it is recognized that the color unevenness is small underevery condition. Moreover, with regard to (5) heat conductivity, as aresult of evaluation targeting 18 W/(m·K) or more from the viewpoint ofa heat radiation effect, it is recognized that the heat conductivity isas high as 24 W/(m·K) under every condition.

For the ceramics composites in Examples 31 to 75, when the lineartransmittance at 600 nm was regulated so as to be ±0.2% or less, thechromaticity variation (ΔCIE_(x)) was 0.001 or less in every case andthus the chromaticity variation could be further suppressed.

From the aforementioned evaluation results, it is recognized that theceramics composites according to the invention are suitable as phosphorsto be used together with blue LED in white LED since the chromaticityvariation is suppressed by the CeAl₁₁O₁₈ phase, the emission intensityof the required yellow fluorescence is high, and the heat conductivityis also high.

While the invention has been described in detail with reference tospecific embodiments thereof, it will be apparent to one skilled in theart that various changes and modifications can be made therein withoutdeparting from the spirit and scope thereof.

Incidentally, the present application is based on Japanese PatentApplications No. 2012-081007 filed on Mar. 30, 2012 and No. 2012-211637filed on Sep. 26, 2012, and the contents are incorporated herein byreference. All references cited herein are incorporated by referenceherein in their entirety.

Also, all the references cited herein are incorporated as a whole.

DESCRIPTION OF REFERENCE NUMERALS AND SIGNS

-   1 Ceramics composite-   2 Matrix phase-   3 Main phosphor phase-   4 CeAl₁₁O₁₈ phase

What is claimed is:
 1. A ceramics composite comprising: a matrix phasecomprising Al₂O₃ or a substance in which one selected from Sc₂O₃ andGa₂O₃ is incorporated into Al₂O₃; a main phosphor phase formed in thematrix phase and comprising a substance represented by a general formulaA₃B₅O₁₂:Ce in which A is at least one selected from Y, Gd, Tb, Yb and Luand B is at least one selected from Al, Ga and Sc; and a CeAl₁₁O₁₈ phasemixed in the matrix phase and the main phosphor phase.
 2. A ceramicscomposite comprising: a matrix phase comprising Al₂O₃ or a substance inwhich one selected from Sc₂O₃ and Ga₂O₃ is incorporated into Al₂O₃; amain phosphor phase formed in the matrix phase and comprising asubstance represented by a general formula A₃B₅O₁₂:Ce in which A is atleast one selected from Y, Gd, Tb, Yb and Lu and B is at least oneselected from Al, Ga and Sc; and a CeAl₁₁O₁₈ phase which is mixed onlyin the main phosphor phase and is present in higher density with aprescribed thickness at an outer peripheral part than at an inner partof the main phosphor phase and which is contained in an amount of 0.5 to5.0% by volume in a total volume of the ceramics composite.
 3. Theceramics composite according to claim 2, wherein the prescribedthickness of the CeAl₁₁O₁₈ phase is 0.1 to 1.9 μm.